Intraoperative field flooding with warm humidified CO2 may help to prevent adhesion formation after open surgery

Modeling open surgery in mice to explore peritoneal damage, carbon dioxide humidification and desmoidogenesis

Background

The exposure of the peritoneum to desiccation during surgery generates lasting damage to the mesothelial lining which impacts inflammation and tissue repair. We have previously explored open abdominal surgery in mice subjected to passive airflow however, operating theatres employ active airflow. Therefore, we sought an engineering solution to recapitulate the active airflow in mice. Similarly, to the passive airflow studies we investigated the influence of humidified-warm carbon dioxide (CO₂) on this damage in the context of active airflow. Additionally, we addressed the controversial role of surgery in exacerbating desmoidogenesis in a mouse model of familial adenomatous polyposis.

Methods

An active airflow mouse-operating module manufactured to produce the equivalent downdraft airflow to that of a modern operating theatre was employed. We quantified mesothelial cell integrity by scanning electron microscopy (SEM) sampled from the peritoneal wall that was subjected to mechanical damage or not, with and without the delivery of humidified-warm CO₂. To explore the role of open and laparoscopic surgery in the process of desmoidogenesis we crossed Apc^min/+ C57Bl/6 mice with p53^+/− mice to generate animals that developed desmoid tumors with 100% penetrance.

Results

One hour of active airflow generates substantial damage to peritoneal mesothelial cells and their microvilli as measured at 24 h post intervention, which is significantly greater than that generated by passive airflow. Use of humidified-warm CO₂ mostly protects the mesothelium that had not experienced additional mechanical (surgical) damage at 24 h. Maximal damage was evident in all treatment groups regardless of flow or use of gas. At day 10 mechanically-damaged peritoneum remains in mice but is essentially repaired in the gas-treated groups. Regarding desmoidogenesis, operating procedures did not increase the frequency of desmoid tumors but their frequency correlated with time following surgery but not age of mice.

Conclusions

Active airflow generates more peritoneal damage than passive airflow and is reduced significantly by the use of humidified-warm CO₂. Introduced peritoneal damage is largely repaired in mice by day 10 with gas. Desmoid tumor incidence is not increased substantially by surgery itself but rises over time following surgery compared to non-surgery mice.

Experimental study of delivery of humidified-warm carbon dioxide during open abdominal surgery

Background

The aim of this study was to monitor the effect of humidified‐warm carbon dioxide (HWCO₂) delivered into the open abdomen of mice, simulating laparotomy.

Methods

Mice were anaesthetized, ventilated and subjected to an abdominal incision followed by wound retraction. In the experimental group, a diffuser device was used to deliver HWCO₂; the control group was exposed to passive air flow. In each group of mice, surgical damage was produced on one side of the peritoneal wall. Vital signs and core temperature were monitored throughout the 1‐h procedure. The peritoneum was closed and mice were allowed to recover for 24 h or 10 days. Tumour cells were delivered into half of the mice in each cohort. Tissue was then examined using scanning electron microscopy and immunohistochemistry.

Results

Passive air flow generated ultrastructural damage including mesothelial cell bulging/retraction and loss of microvilli, as assessed at 24 h. Evidence of surgical damage was still measurable on day 10. HWCO₂ maintained normothermia, whereas open surgery alone led to hypothermia. The degree of tissue damage was significantly reduced by HWCO₂ compared with that in controls. Peritoneal expression of hypoxia inducible factor 1α and vascular endothelial growth factor A was lowered by HWCO₂. These effects were also evident at the surgical damage sites, where protection from tissue trauma extended to 10 days. HWCO₂ did not reduce tumorigenesis in surgically damaged sites compared with passive air flow.

Conclusion

HWCO₂ diffusion into the abdomen in the context of open surgery afforded tissue protection and accelerated tissue repair in mice, while preserving normothermia.

Role of the peritoneal cavity in the prevention of postoperative adhesions, pain, and fatigue

A surgical trauma results within minutes in exudation, platelets, and fibrin deposition. Within hours, the denuded area is covered by tissue repair cells/macrophages, starting a cascade of events. Epithelial repair starts on day 1 and is terminated by day 3. If repair is delayed by decreased fibrinolysis, local inflammation, or factors in peritoneal fluid, fibroblast growth starting on day 3 and angiogenesis starting on day 5 results in adhesion formation. For adhesion formation, quantitatively more important are factors released into the peritoneal fluid after retraction of the fragile mesothelial cells and acute inflammation of the entire peritoneal cavity. This is caused by mechanical trauma, hypoxia (e.g., CO₂ pneumoperitoneum), reactive oxygen species (ROS; e.g., open surgery), desiccation, or presence of blood, and this is more severe at higher temperatures. The inflammation at trauma sites is delayed by necrotic tissue, resorbable sutures, vascularization damage, and oxidative stress. Prevention of adhesion formation therefore consists of the prevention of acute inflammation in the peritoneal cavity by means of gentle tissue handling, the addition of more than 5% N₂O to the CO₂ pneumoperitoneum, cooling the abdomen to 30°C, prevention of desiccation, a short duration of surgery, and, at the end of surgery, meticulous hemostasis, thorough lavage, application of a barrier to injury sites, and administration of dexamethasone. With this combined therapy, nearly adhesion-free surgery can be performed today. Conditioning alone results in some 85% adhesion prevention, barriers alone in 40%-50%.

Humidification during laparoscopic surgery: overview of the clinical benefits of using humidified gas during laparoscopic surgery

PURPOSE

The peritoneum is the serous membrane that covers the abdominal cavity and most of the intra-abdominal organs. It is a very delicate layer highly susceptible to damage and it is not designed to cope with variable conditions such as the dry and cold carbon dioxide (CO2) during laparoscopic surgery. The aim of this review was to evaluate the effects caused by insufflating dry and cold gas into the abdominal cavity after laparoscopic surgery.

METHODS

A literature search using the Pubmed was carried out. Articles identified focused on the key issues of laparoscopy, peritoneum, morphology, pneumoperitoneum, humidity, body temperature, pain, recovery time, post-operative adhesions and lens fogging.

RESULTS

Insufflating dry and cold CO2 into the abdomen causes peritoneal damage, post-operative pain, hypothermia and post-operative adhesions. Using humidified and warm gas prevents pain after surgery. With regard to hypothermia due to desiccation, it can be fully prevented using humidified and warm gas. Results relating to the patient recovery are still controversial.

CONCLUSIONS

The use of humidified and warm insufflation gas offers a significant clinical benefit to the patient, creating a more physiologic peritoneal environment and reducing the post-operative pain and hypothermia. In animal models, although humidified and warm gas reduces post-operative adhesions, humidified gas at 32 °C reduced them even more. It is clear that humidified gas should be used during laparoscopic surgery; however, a question remains unanswered: to achieve even greater clinical benefit to the patient, at what temperature should the humidified gas be when insufflated into the abdomen? More clinical trials should be performed to resolve this query.

To perform operative procedures in an optimized local atmosphere: can it reduce post-operative adhesion formation?

BACKGROUND

Adhesion formation is a major problem following abdominal surgery as it creates a considerable economic burden in addition to an increased risk for complications. In the present study, an effort was made to reduce post-operative adhesion formation by creating an artificial atmosphere within and around the abdominal cavity during an open surgical procedure.

METHODS

82 Wistar male rats (Clr:WI) (200 gr, 7 weeks) were randomized into two groups. The abdominal cavity of the control group was exposed to the normal atmosphere of the operating-theatre during surgery (21% O₂, 21 °C, 40-47% relative humidity (RH)), while the abdominal cavity of the study group was exposed to an artificial atmosphere during surgery (3-6% O₂, >75% CO₂, 95-100% RH, 37 °C). Adhesion induction consisted of a laparotomy along linea-alba, four lesions in the anterior abdominal-wall, blood from the tail vein dripped inside the abdominal cavity and exposure to the atmosphere around the wound by use of self-retaining retractors. In addition, a liquid-sample for quantitative bacteriologic cultivation and bacterial load (CFU/ml) calculation was taken just before closure. After 3 weeks the abdominal cavity was scored for the extent, tenacity and severity of adhesions before the rats were euthanized. The two-sample-Wilcoxon-rank-sum test was used in the analysis.

RESULTS

Highly significant differences in postoperative total adhesion score, extent-, severity- and tenacity-score were found (P < 0.01). No differences were found between the two groups regarding mean bacterial load (P > 0.05).

CONCLUSIONS

The rats exposed to the warmed and humidified artificial atmosphere consisting of more than 75% carbon dioxide and 3-4% oxygen during surgery had more severe and more post-operative adhesions compared to the rats that were exposed to the ambient air during surgery.

The influence of pre-emptive analgesia on postoperative analgesia and its objective evaluation

INTRODUCTION

The evaluation of pain intensity is still a subject of research. Mostly psychological evaluations are used. We started to conduct biochemical evaluation in animal experiments. Now we present biochemical evaluation in postoperative pain in man.

MATERIAL AND METHODS

In 67 patients herniotomy was done. For pre-emptive analgesia morphine and pethidine were used and the following indicators were measured: visual analogue scale (VAS), measurement of lipid spectra, saccharides and proteins, thioredoxin, super-oxide dismutase (SOD), glutathione peroxidase (GPx) and NAD(P)H-oxidase (NOX), and free radicals using electron paramagnetic resonance (EPR). Blood samples were taken and tested: before pre-medication and intervention, 4 h after and 24 h after intervention.

RESULTS

Free radicals (FR) increased in individual samples during the postoperative course in pethidine and without pre-medication. After application of morphine the FR were insignificantly reduced. Statistically significant differences were found in albumin, prealbumin, apolipoprotein A, total cholesterol, atherosclerotic index, CRP, glucose, and thioredoxin (p ≤ 0.001). A greater difference was seen in VAS values between morphine and pethidine premedications (p ≤ 0.001).

CONCLUSIONS

It was proved that the biochemical markers of lipid, protein and saccharide metabolisms and free radicals as well as singlet oxygen can serve as very good indicators of the intensity of pain and nociception. In patients it was proved that pre-emptive analgesia plays an important role in reducing the intensity of postoperative pain. From the three modalities of pre-emptive analgesia morphine represents the best solution.